<div class="maxdiv">
     <div class="header">
     <h1>博客后台管理首页</h1>
     <?php
      session_start();
     if(!isset($_SESSION['username'])){
      header("Location:log.php");
      exit();
       }else{
        ?>
        <a href="out.php" class="layui-btn ">退出</a> 
         <a href="" class="layui-btn ">欢迎你,管理员<?php echo $_SESSION['username']?></a>
         <?php
       }
        ?>
     </div> 
  </div>